- #1
salpal243
- 2
- 0
the question I am stumped on is "What is the lift force on the roof of your car that has an aera of 3.9m^2 if you are driving 100km/hr? use 1.17kg/m^3 for density of air
rcgldr said:Speed alone isn't going to create lift on a flat plate parallel to the relative wind. Bernoulli principle doesn't apply here. You could place a flush mounted static port in a flat roof to measure pressure of the moving air outside and it would indicate the same ambient pressure if the car was stopped or moving (as long as speeds are reasonably sub-sonic).
rcgldr said:Speed alone isn't going to create lift on a flat plate parallel to the relative wind.
Because the speed of the air wasn't the result of a transition from higher pressure to lower pressure. In this case, the assumption is that the pressure of the air is ambient. It doesn't matter what the speed of the flat plate is if the flat plate isn't interacting with the air (assume the flat plate doesn't change the speed of the air, ignoring any skin friction effects). This why static ports that are just small openings in the side of an aircraft's fuselage (at a point where the air's speed isn't being changed) can sense the ambient pressure of the air, regardless of the speed of the aircraft (as long as speed is sufficiently below the speed of sound).Lsos said:Why does Bernoulli principle not apply?
Lift force on the roof of a car is the upward force that is exerted on the roof of a car due to air resistance while the car is in motion. This force is caused by the difference in air pressure above and below the roof of the car.
Lift force is important for cars because it affects the overall aerodynamics and stability of the vehicle. Too much lift force can cause a car to become unstable and difficult to control, while too little lift force can decrease fuel efficiency and performance.
The shape and design of the car's roof, the speed of the car, the angle of the roof, and the density of the air are all factors that can affect the lift force on a car's roof. Additionally, any objects or attachments on the roof can also impact the lift force.
Lift force on the roof of a car is calculated using the formula F = (1/2) * ρ * v^2 * A * CL, where F is the lift force, ρ is the air density, v is the velocity of the car, A is the area of the roof, and CL is the coefficient of lift.
To reduce lift force on the roof of a car, the design of the car can be modified to decrease the angle of the roof and create a more streamlined shape. Additionally, removing any objects or attachments on the roof can also reduce lift force. Other methods include adding spoilers or air dams, or adjusting the suspension to lower the car's height.